This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A378057 #7 Nov 15 2024 12:56:40
%S A378057 6,481,793,949,1417,2041,2257,2509,2701,2977,3133,3589,3601,4033,4069,
%T A378057 4453,4849,5161,5317,5809,5917,5941,6697,7033,7081,7141,7501,7957,
%U A378057 7969,8593,8917,9217,9529,9577,10249,10573,10777,11041,11401,11461,11581,11773,12469,12913,12961
%N A378057 Composite numbers k such that A378056(k) = gcd(lcm{d+1 : d|k}, lcm{d-1 : d > 1 and d|k}) = 2.
%C A378057 A378056(p) = 2 for all odd primes p.
%C A378057 6 is the only even term.
%C A378057 The least term that is not a semiprime is a(114) = 29341 = 13 * 37 * 61, and the least term that has more than 3 distinct prime factors is a(4087545) = 1038565321 = 37 * 61 * 421 * 1093.
%H A378057 Amiram Eldar, <a href="/A378057/b378057.txt">Table of n, a(n) for n = 1..10000</a>
%t A378057 s[n_] := Module[{d = Divisors[n]}, GCD[LCM @@ (d + 1), LCM @@ (Rest @ d - 1)]]; s[1] = 1; Select[Range[13000], CompositeQ[#] && s[#] == 2 &]
%o A378057 (PARI) is(k) = if(isprime(k), 0, my(d = divisors(k)); gcd(lcm(apply(x->x+1, d)), lcm(apply(x -> if(x > 1, x-1, x), d))) == 2);
%Y A378057 Cf. A378056.
%K A378057 nonn
%O A378057 1,1
%A A378057 _Amiram Eldar_, Nov 15 2024